Still planning for some shelf units. I built a simple jig for routing out the dadoes. I cheated a bit, leaving out the adjustability for now, but I'm quite pleased with the results. The test dadoes are nice and snug and the process is very quick.
The scrap ply that I used to test the jig happened to be finished; I guess it was a shelf for an older project. I was impressed by how cleanly the router cut the dadoes. It has me wondering if there would be any problem with prefinishing the uprights and routing the dadoes afterward. I had already planned to prefinish the pieces before assembly, but this would eliminate the need to mask (or otherwise avoid) the insides of the dadoes during the finishing process.